New York – Alexandria Ocasio-Cortez surprised herself. And a lot of other people, too.

The 28-year-old liberal activist, who worked as a bartender at times last year, knocked off the No. 4 House Democrat Tuesday in New York City. And in so doing, the former Bernie Sanders campaign organizer threw a spotlight on the surge of energy on the left that's re-defining the Democratic Party's search for a new identity in the age of Donald Trump.

"We always thought it was possible," Ocasio-Cortez said of her win against 10-term incumbent Joe Crowley in an interview Wednesday with The Associated Press. She added: "I just felt like we could do so much better, and we could be so much better."

But hardly clearer for the party.

Her stunning victory in the Democratic primary offers a new window into the tug-of-war for the direction of the party as Trump's presidency stretches through its second year, a fight often overshadowed by the more explosive intraparty debate on the Republican side.

Ocasio-Cortez's unlikely win elevated the Democratic Party base's leftward lurch on some issues — the embrace of Medicare for all and the abolition of the federal agency that enforces immigration laws, among them — even if the party's establishment leaders are reluctant to promote such liberal priorities as Democrats fight for control of Congress this fall.

Some party leaders fear that Ocasio-Cortez and her Sanders-style message could alienate voters in key races this fall where vulnerable Democrats must appeal to conservative Democrats and even some Republicans.

The GOP was more than happy to highlight Ocasio-Cortez's victory, with the Republican National Committee blasting out a can-you-believe-it statement about Democrats moving "drastically to the left" as they "elected a self-avowed socialist."

House Minority Leader Nancy Pelosi was quick to declare that while Ocasio-Cortez's New York City district may be moving to the left, it's not necessarily a sign of a broader shift within her party.

"Nobody's district is representative of somebody else's district," Pelosi said.

The response was just the opposite for liberal leaders such as Sanders and for Trump-resistance groups such as Indivisible and MoveOn.

"What Alexandria did was really quite unbelievable. It tells me that the political revolution is alive and well and spreading all across this country," Sanders said in an interview.

Ocasio-Cortez's embrace of Medicare for all, a $15 minimum wage and a new immigration system, Sanders said, is exactly the kind of message needed to energize Democratic voters across the country.

Yet the Vermont senator stopped short of agreeing with Ocasio-Cortez's call to abolish the department of Immigration and Customs Enforcement.

"I understand completely that people in their total disgust with what the Trump administration is doing are calling for the abolition of ICE," Sanders said. "I think what we've got to do is abolish the entire ugly immigration policy that exists right now and move toward immigration reform, comprehensive immigration reform."

Sanders, who is 76 and hasn't said whether he'll make a second presidential run in 2020, insisted the new direction of the party should focus on progressive policies.

But Former Vermont Gov. Howard Dean, a former presidential contender himself, took away a very different lesson from Ocasio-Cortez's win.

"I don't think this has anything to do with ideology; I think this has to do with generations," Dean said in an interview. "I don't want to support anybody who's over 50, 55 in the presidential race. It's time for a new generation to take over. This generation is taking over."

Victories by liberal Democrats in House primaries is a sign of Democratic enthusiasm, especially in swing-voting or GOP-leaning districts where establishment Democrats have assumed voters prefer incremental changes, said Adam Green, of the Progressive Change Campaign Committee.